Interpopulation variability and adaptive potential for reduced glyphosate sensitivity in Alopecurus myosuroides

Area of Science:

• Agricultural Science
• Plant Science
• Weed Science

Background:

• Glyphosate use has doubled in the UK over 20 years, primarily for managing herbicide-resistant weeds like black-grass (Alopecurus myosuroides).
• Concerns exist regarding the long-term sustainability of glyphosate due to potential resistance evolution.

Purpose of the Study:

• To investigate the variation in glyphosate sensitivity among field-collected black-grass populations.
• To determine if glyphosate sensitivity in black-grass has a heritable basis and assess the potential for resistance evolution.

Main Methods:

• Dose-response experiments were conducted on 40 field-collected Alopecurus myosuroides populations.
• Recurrent selection experiments were performed to assess the heritability of glyphosate sensitivity.

Main Results:

• No populations exhibited resistance to glyphosate, with ED90 values ranging from 354 to 610 g a.i. ha⁻¹.
• Five populations showed significantly higher ED90 values than a glyphosate-naïve control population.
• Following two selection rounds, five of six populations evolved reduced glyphosate sensitivity (R/S ratios 1.2–1.5).

Conclusions:

• A heritable basis for variation in glyphosate sensitivity exists in Alopecurus myosuroides.
• While the response to selection was modest, evolved populations showed reduced sensitivity, warranting caution for sustainable glyphosate use.